A nano-composite of magnetite and hot-water-soluble starch: a cooperation resulting in an amplified catalytic activity on water

Abstract

Bis-coumarins and xanthenes are privileged compounds with diverse pharmaceutical activities. Hence, we introduce here an efficient synthesis of 3,3′-arylmethylene-bis-(4-hydroxycoumarin-3-yl) and 1,8-dioxooctahydroxanthenes under the soft catalytic activity of magnetite encapsulated hot-water-soluble starch nanoparticles. The greater catalytic efficiency of the bio-derived nano-composite in these syntheses over magnetite and hot-water-soluble starch was ascribed to cooperation of its two components in proton exchange with the reactants. The enhanced proton exchange of the nano-composite was better interpreted as being conducted by its bioorganic shell through switching between the covalent and the coordination bonds it forms with the magnetite core. Application of a nontoxic and superparamagnetic bio-consistent catalyst, simple work-up procedure, and short reaction times are the prominent advantages of the synthetic methods presented here. The nano-catalyst is stable, as it can be recycled in the model reactions at least four times without appreciable decrease in its catalytic activity.